Because a vacuum insulator has an excellent insulating performance, it is used in various devices for cold reserving and heat reserving. In a conventional vacuum insulator, although glass fibers obtained by a centrifugal method or a flame method are mainly used as a core member, but a continuous filament method having good linearity of fibers and excellent fiber orientation is also used (for example, see Patent document 1). For example, the core member is fabricated by overlapping a plurality of pieces of inorganic non-woven fabric.
In addition, inorganic fibers whose partial fibers are bundled, and a binder component for binding the fibers are also used as composition materials so as to obtain a high-density inorganic non-woven fabric (for example, see Patent document 2).
In addition, there is a base-material non-woven fabric for fiberglass reinforced plastics (FRP), which includes a fiber filament obtained by bundling 100 or more fibers and whose content is 20 weight percent or more, so as to improve shock resistance, and that is obtainable using a binder having a glass transition point of 30° C. or less (for example, see Patent document 3).